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Partial dependence plots to show the effect of the degree of habitat fragmentation, the degree of patch isolation, and the matrix condition on extinction risk transitions in terrestrial mammals The plots show the probability of high-risk transitions as a function of a the degree of fragmentation, b the degree of patch isolation, and c the extent of high human footprint values within the matrix. Solid red lines and shading represent fitted LOESS curves and 95% credible intervals for the relationships between the probability of high-risk transitions and each explanatory variable. As partial dependence plots for Boolean response variables mirror each other, the probability of low-risk transitions as a function of these variables are not depicted in the figure. Values of the degree of fragmentation and the degree of patch isolation were ln-transformed for visual purposes. The degree of fragmentation was inverse-coded so high values represent high degrees of fragmentation. High values of the degree of patch isolation represent high degrees of isolation between patches of suitable habitat. The description of each variable is given in Table 1. High levels of the human footprint (HFP) included values of 3 or above. Source data are provided as a Source Data file.
Source publication
Habitat loss is the leading cause of the global decline in biodiversity, but the influence of human pressure within the matrix surrounding habitat fragments remains poorly understood. Here, we measure the relationship between fragmentation (the degree of fragmentation and the degree of patch isolation), matrix condition (measured as the extent of h...
Citations
... Finally, we demonstrated that relief amplitude and normalized difference vegetation index were negatively correlated with species richness when the human footprint index was high (HFI > 40, Fig. 3), while being positively correlated in other areas, indicating that human activity might alter the positive or negative impacts of variables depending on the species community and other correlated variables. Thus, our results do not support findings showing that species occurring in regions with less historical anthropogenic disturbance are more susceptible to environment changes (Ramírez-Delgado et al., 2022). Indeed, human activities have a lower effect on amphibian species diversity than environment factors when studied at a large geographic scale (Howard et al., 2020;Lu et al., 2020), while anthropogenic impacts have a significantly negative effect on amphibian biodiversity within small geographic areas (Ficetola and De Bernardi, 2004;Hamer et al., 2021). ...
Despite the variation in amphibian biodiversity being often explained through environmental variables, the effects of spatial non-stationarity factors are too-often ignored as significant geographic characteristics, especially at large scales. Here, using a spatial regression approach through a multiscale analysis, we explored the spatial heterogeneity and scale effects in the impacts of environments on amphibian species richness across China. We showed that the impacts of variables varied with regions, and the individual scales specific to each variable were negatively correlated with effect sizes. We then demonstrated that climate variables, followed by topography, showed a high explanatory power for species richness in most areas, while the effects of precipitation and temperature were characterized by high geographical heterogeneity. In addition, elevation was positively related to local species richness in most plains, while being a main negative variable to species richness in the western highlands. The analysis of geographic heterogeneity showed that the explanatory power of most variables declined with increasing elevation. Although anthropogenic impacts contributed less than climatic variables, they significantly increased the sensitivity of amphibian species to environmental variations. Finally, to measure the aggregation pattern of heterogeneous effects of variables on species richness, we used a neural network to identify ecoregions regulated by similar variables and determined the presence of four ecologically consistent regions. Our findings provide further evidence supporting spatially variables regulators of amphibian diversity.
... Some studies have argued that habitat fragmentation generally has no, or even positive, effects on species richness and abundance (Fahrig 2019;Fahrig et al. 2019), while others support the traditional view that habitat configuration, irrespective of habitat amount, yields negative effects on species persistence (Haddad et al. 2015;Fletcher et al. 2018;Saura 2020). In this work we show that fragmentation, either expressed as mean patch area or distance from edge, is positively related to the extinction risk of neotropical primates, and these measures interact negatively with the amount of habitat area, reinforcing the idea that habitat configuration, not just amount, is a key parameter for species persistence (Ramírez-Delgado et al. 2022) particularly in the case of habitat specialists with limited mobility across non-habitat areas such as arboreal primates. ...
Habitat fragmentation and overexploitation of natural resources are the most prevalent and severe threats to biodiversity in tropical forests. Several studies have estimated the effect of these threats on species extinction risk, however the effect resulting from their interaction remains poorly understood. Here, we assess whether and how habitat area, fragmentation, and hunting can synergistically affect the extinction risk of neotropical primates (Platyrrhine). We use a Random Forest model to estimate the Red List extinction risk category of 147 primate species based on their biological traits and the environmental predictors they are exposed to. We find that environmental variables are better predictors of extinction risk than biological traits, and that hunting and fragmentation interact creating synergistic feedback that lead to higher extinction risk than when considered in isolation. We also show that the effect of environmental predictors is mediated by biological traits, with large species being sensitive to habitat area and fragmentation, and frugivorous species more threatened by hunting. Our results increase the understanding of potentially interactive effects between different threats, habitat area and species traits, supporting the idea that multiple threats can reinforce each other and should be thus addressed simultaneously in conservation agendas.
... The habitat of organisms is crucial for characterizing their life history and can influence the distribution, abundance, and survival rate of species (Potts et al., 2020). Of the many reasons, human-caused habitat loss or frag-mentation significantly risks the species' survival; therefore, understanding appropriate habitat conditions and the variables that influence the species' habitat is crucial for conserving threatened species (Ramírez-Delgado et al., 2022). From an ecological perspective, environmental predictors can limit the spread of organisms and alter habitat suitability (Fournier et al., 2017). ...
The Tibetan Plateau is home to the only alpine crane species, the black-necked crane (Grus nigricollis). Conservation efforts are severely hampered by a lack of knowledge on the spatial distribution and breeding habitats of this species. The ecological niche modeling framework used to predict the spatial distribution of this species, based on the maximum entropy and occurrence record data, allowed us to generate a species-specific spatial distribution map in Ladakh, Trans-Himalaya, India. The model was created by assimilating species occurrence data from 486 geographical sites with 24 topographic and bioclimatic variables. Fourteen variables helped forecast the distribution of black-necked cranes by 96.2%. The area under the curve score for the model training data was high (0.98), indicating the accuracy and predictive performance of the model. Of the total study area, the areas with high and moderate habitat suitability for black-necked cranes were anticipated to be 8,156 km 2 and 6,759 km 2 , respectively. The area with high habitat suitability within the protected areas was 5,335 km 2. The spatial distribution predicted using our model showed that the majority of speculated conservation areas bordered the existing protected areas of the Changthang Wildlife Sanctuary. Hence, we believe, that by increasing the current study area, we can account for these gaps in conservation areas, more effectively. ABSTRACT Original Article PNIE 2023;4(2):79-85
... High rates of fragmentation may also lead to a loss of connectivity, affecting populations. Population connectivity influences functional ecology and is related to the ability of species to persist and recover from ecological perturbations such as habitat fragmentation and climate change [3]. Loss of connectivity, coupled with climate change, can be terrible for biodiversity. ...
This study investigates the impact of fragmentation on Ecuador’s coastal mangrove forests. Fragmentation is identified as a primary cause of aquatic ecosystem degradation. We analyzed the relationship between habitat loss, fragmentation, and mangrove connectivity through a multitemporal approach using Global Mangrove Watch and fragmentation and connectivity metrics. The terrain was divided into 10 km2 hexagons, and six fragmentation metrics were calculated. A Getis–Ord Gi* statistical analysis was used to identified areas with the best and worst conservation status, while connectivity analyses were performed for a generic species with a 5 km dispersion. Findings revealed widespread mangrove fragmentation in Ecuador, with geographical differences between the insular region (Galapagos) and the mainland coast. Minimal loss or even expansion of mangrove forests in areas like the Galapagos Islands contrasted with severe fragmentation along the mainland coast. Transformation of forests into fisheries, mainly prawn factories, was the primary driver of change, while only a weak correlation was observed between mangrove fragmentation and conversion to agriculture, which accounts for less than 15% of all deforestation in Ecuador. Fragmentation may increase or decrease depending on the management of different deforestation drivers and should be considered in large-scale mangrove monitoring. Focusing only on mangrove deforestation rates in defining regional conservation priorities may overlook the loss of ecosystem functions and fragmentation.
... There is general agreement that the amount of natural habitat remaining in a landscape is the single most important determinant of species persistence there, and by contrast, the amount of habitat lost is the most significant threat to native species (Wilcox, 1980;Fahrig, 2017;Watling et al., 2020). However, the impact of how the remaining habitat is distributed (i.e., whether more or less fragmented for any given habitat amount) is still the topic of vigorous debate, termed the Habitat Area Hypothesis (Fahrig, 2017;Fletcher et al., 2018;Fahrig et al., 2019;Pablo Ramírez-Delgado et al., 2022). Further, there is growing understanding that the "matrix" surrounding natural and semi-natural habitat patches greatly influences biodiversity outcomes, by acting either as a barrier or conduit to species movements, providing complementary resources or habitat for some species while acting as an ecological trap or sink for others, and influencing the abiotic and biotic environments of the remaining natural habitat patches (Driscoll et al., 2013). ...
... It has further been acknowledged that land-sparing land-sharing studies add an important but not the sole needed component to determine the best outcomes for biodiversity and people (Phalan, 2018). While many of the early social critiques are acknowledged by both sides as important, more of the ecological issues remain controversial, such as the role of the matrix in maintaining connectivity and long-term persistence for biodiversity (Kremen and Merenlender, 2018;Phalan, 2018;Brennan et al., 2022;Pablo Ramírez-Delgado et al., 2022), an area which remains understudied. Strikingly, the same evidence is sometimes used to indicate support for sparing or for sharing; for example intensive silvopastoral systems, push-pull strategies and promoting pollination mentioned in Balmford (2021) to support land sparing, and in Kremen (2020) to support ecological intensification and agricultural diversification, suggesting that more convergence will emerge as meanings and scales are increasingly clarified. ...
... While of course the impact of matrix quality is species-specific, several new studies use the human footprint index (HFI; Venter et al., 2016) to demonstrate the importance of the matrix for mammalian species persistence and movement. A study of 4426 mammalian species showed that extinction risks over 24 years in low-quality matrices (high HFI) were greatly influenced by the degree of habitat fragmentation and isolation; whereas these variables were much less important in high-quality matrices (low HFI;Delgado et al., 2022). Modeling functional connectivity of the world's protected areas based on mammalian movements and their relationship to HFI revealed that interventions that reduce the HFI score (i.e., improving matrix quality) would be twice as effective at reducing protected area isolation than would increasing size of the protected area estate (Brennan et al., 2022). ...
... Our analysis showed that paleochannels are highly fragmented by cropland and roads that interrupt their continuity (Table 1 and Fig. A.7, see Appendix). Because the fragmentation process creates new edges in paleochannel units, the highly transformed matrices could exert a negative effect on the cover of paleochannel units by lowering the effective area of grasslands (Ramírez-Delgado et al., 2022;Saunders, Hobbs, & Margules, 1991) and promoting their rapid conversion to cultivated landscapes or livestock systems . Indeed, our results showed that as matrix transformation increased, cropland cover within paleochannels and their fragmentation also increased (Fig. 3b). ...
... We highlighted units with high conservation value in medium transformation matrices because (1) most were not included in any protection scheme, and (2) their high productivity makes them most prone to be transformed into agricultural landscapes. Indeed, Ramírez-Delgado et al. (2022) suggested that habitat fragmentation and the matrix condition better predict changes in species extinction risk than habitat loss and habitat amount at a global level. Therefore, habitat matrix restoration could be a relevant conservation action to reduce the effect of fragmentation on the paleochannels and their biodiversity. ...
... Besides, to preserve the grassland of the region, we need to include the effects of the matrix on the fragmentation and productivity of the grassland units. In other words, the matrix should be treated as a heterogeneous mosaic with different land covers and land uses (Ramírez-Delgado et al., 2022). Furthermore, the loss of diverse habitats within the dryland system, such as the Dry Chaco, boosts its continuous long-term transformation, homogenization, and thus loss of ecological resilience to global change. ...
Subtropical drylands, such as the South American Dry Chaco, harbor azonal grasslands in ancient river beds (hereafter, paleochannels). These grasslands host high biodiversity and provide numerous ecosystem services. However, cultivated systems often replace paleochannels grasslands due to their biophysical characteristics and low investment requirements. Furthermore, there is a lack of basic characterization of paleochannel grasslands due to their complexity, which challenges their conservation. Here, we mapped and described for the first time the paleochannel grasslands of the Argentinean Dry Chaco based on their current land cover, spatial configuration, EVI values (a proxy for primary productivity), fragmentation, and protection. We speculate that natural (i.e., shrub encroachment enhanced by overgrazing and fire management prohibition) and anthropogenic processes (i.e., farming and infrastructure) have transformed the Argentinean Dry Chaco grasslands into woody-dominated or agricultural systems. Therefore, while grasslands in low-transformation matrices were mainly replaced by shrubs, those in high-transformation matrices were integrated into agricultural landscapes (i.e., whole units fragmented by croplands and roads). However, paleochannels in medium-transformation matrices showed the highest grassland cover, EVI values, and intermediate fragmentation level. Located in the NW of the Argentinean Dry Chaco, this group of paleochannels should be prioritized in future conservation and management strategies, as currently is not included in any protection scheme. Our work highlights the need to include non-pristine systems that have received perturbation in the past in conservation actions to mitigate and reduce the degradation of threatened dryland habitats.
... Habitat loss and the subsequent fragmentation results in a wide variety of ecological, environmental, social, and economic impacts [7], and is one of the major components of global change [8]. Fragmentation has been classified as one of the main threats to tropical forests and their associated biodiversity [9,10], and has been strongly associated with the loss of species [11]. It is for these reasons that estimating habitat fragmentation is a relevant ...
... The area of influence (Ai) is based on the maximum area that the patch could occupy if it had not undergone deforestation processes. The (Ap/Ai) section was given a greater weight (4/5) because this section accumulates the worst effects with regard to biodiversity (habitat loss and isolation [11]) and encompasses more metrics than the MPFD section (1/5), which is divided by 2 because it is a value between 1 and 2 [45], while PFI has values of between 0 and 1. In practice, the maximum PFI value of 1 is never reached, as this signifies the disappearance of the patch and, therefore, it has neither area nor shape. ...
... These four metrics are, in order of importance: composition and area, isolation, edge (e.g., the third would be a combination of the first and second), and shape. For their part, Rogan and Lacher [8] considered that these four metrics reflect the main alterations in habitat (the habitat matrix metric has been excluded because it refers to human-modified land that surrounds or intersperses remnant native habitat patches in fragmented landscapes [11]), and have been shown to be useful with regard to describing detrimental effects on plant and animal species. The Patch Fragmentation Index (PFI) proposed in this work is, therefore, a useful and accurate tool with which to measure the patch fragmentation status, because it represents the four key metrics. ...
There are many local fragmentation metrics, but most can be grouped into four types (composition/area, isolation, edge, and shape), and none of them alone determines the degree of fragmentation of a patch. Here, we grouped together the main fragmentation metrics (area, edge, shape, and isolation) in order to propose a new metric/index, the Patch Fragmentation Index (PFI), with which to determine fragmentation at patch scale. The index was subsequently verified with the Ecuadorian seasonal dry forest by employing geographic information layers and temporal land uses changes in 1990, 2000, 2008, and 2018. The PFI was applied to calculate the fragmentation per patch, spatial and temporal changes of fragmentation based on PFI were assessed, and the spatial patterns (Getis-Ord Gi * analysis) were calculated. The Ecuadorian seasonal dry forest obtained a mean PFI value of 0.88 (median = 0.99) in 2018. This value has increased by 8.6% since 1990, and 3451 patches of forest disappeared between 1990 and 2018. The Getis-Ord Gi * analysis was effective with regard to describing the spatial patterns, and 62% of the patches that were classified as hot patches in 1990 had disappeared by 2018. The PFI has proven to be a useful tool with which to describe fragmentation patterns at patch scale (regardless of its size) and can be extrapolated to other landscapes. The PFI will provide a new vision and can help in the decision-making related to the conservation and management of fragmented ecosystems.
... Recent Sumatran extirpations have likely been driven by rapid deforestation for pulp, rubber, and oil palm production, and this deforestation has occurred at a rate faster than Borneo and mainland Southeast Asia (17). Forest fragmentation and landcover changes in the matrix between fragments across vast areas are strongly associated with extinction risk in terrestrial mammals (40). We fear that megafauna extirpations in Sumatra may increase through the Anthropocene because of its growing extinction debt (41), such as on Java where considerably more megafaunal extinctions have accumulated after its longer history of land clearing (42). ...
The “trophic downgrading of planet Earth” refers to the systematic decline of the world’s largest vertebrates. However, our understanding of why megafauna extinction risk varies through time and the importance of site- or species-specific factors remain unclear. Here, we unravel the unexpected variability in remaining terrestrial megafauna assemblages across 10 Southeast Asian tropical forests. Consistent with global trends, every landscape experienced Holocene and/or Anthropocene megafauna extirpations, and the four most disturbed landscapes experienced 2.5 times more extirpations than the six least disturbed landscapes. However, there were no consistent size- or guild-related trends, no two tropical forests had identical assemblages, and the abundance of four species showed positive relationships with forest degradation and humans. Our results suggest that the region’s megafauna assemblages are the product of a convoluted geoclimatic legacy interacting with modern disturbances and that some megafauna may persist in degraded tropical forests near settlements with sufficient poaching controls.
... However, compared to actual islands, forest stands fall along a gradient from effectively continuous populations, to functioning meta-populations with a balance of extinction and (re)colonization, to non-viable meta-populations where sub-populations lose connectivity and slowly disappear [36,37]. The configuration, composition, and history of the surrounding landscape (or matrix) will directly affect where along this gradient a stand sits [29,[38][39][40]. Despite this, the effect of landscape-level variables on stand-level diversity remains underappreciated [12,29,[41][42][43][44][45][46]. ...
Background
Silviculture and land-use change has reduced the amount of natural forest worldwide and left what remains confined to isolated fragments or stands. To understand processes governing species occurrence in such stands, much attention has been given to stand-level factors such as size, structure, and deadwood amount. However, the surrounding matrix will directly impact species dispersal and persistence, and the link between the surrounding landscape configuration, composition and history, and stand-level species occurrence has received insufficient attention. Thus, to facilitate optimisation of forest management and species conservation, we propose a review addressing ‘To what extent does surrounding landscape explain stand-level occurrence of conservation-relevant species in fragmented boreal and hemi-boreal forest?’.
Methods
The proposed systematic review will identify and synthesise relevant articles following the CEE guidelines for evidence synthesis and the ROSES standards. A search for peer-reviewed and grey literature will be conducted using four databases, two online search engines, and 36 specialist websites. Identified articles will be screened for eligibility in a two-step process; first on title and abstract, and second on the full text. Screening will be based on predefined eligibility criteria related to a PECO-model; population being boreal and hemi-boreal forest, exposure being fragmentation, comparator being landscapes with alternative composition, configuration, or history, and outcome being occurrence (i.e., presence and/or abundance) of conservation-relevant species. All articles that pass the full-text screening will go through study validity assessment and data extraction, and be part of a narrative review. If enough studies prove comparable, quantitative meta-analyses will also be performed. The objective of the narrative review and the meta-analyses will be to address the primary question as well as six secondary questions, and to identify important knowledge gaps.
... In addition, the habitat types in biodiversity maintenance areas are highly diverse, and ecological corridors between ecological sources should be established. It is also important to consider the habitat islands of key species, and the regional biodiversity can be protected by reducing the fragmentation degree of habitats (Chase et al., 2020;Ramírez-Delgado et al., 2022). ...
The establishment of scientific and reasonable ecological function regionalization (EFR) plays an important role in giving full play to regional advantages and realizing the benign development of resource exploitation, ecological construction, and environmental protection. However, the existing EFR lacks the identification ability for the leading functions among various ecological functions, and it is difficult to determine the regional ecological advantages, which may hinder the practical application of EFR in ecological environment zoning management. In view of this, we propose a new leading ecological function (LEF) index and the corresponding calculation method to describe the main regional ecosystem services and functions; its application in EFR could enhance the regional spatial guidance effect. We took the Core Area of the Beijing-Hangzhou Grand Canal (CA-BHGC) in China as the study area and used the maximum value composite (MVC) method to identify the LEFs of acquired grid pixels. Furthermore, the LEFs of grid pixels were applied to county-level administrative regions to complete the EFR process. Based on the results, in the CA-BHGC, although the spatial distribution of ecological function values was extremely uneven, the contribution rate of the LEF of grid pixels to the comprehensive ecological function value was usually more than 50%, reliably representing the advantageous ecological functions of grid pixels. The LEFs of the CA-BHGC included biodiversity maintenance, food production, and water retention, with grid proportions of 51.64%, 41.04%, and 6.93%, respectively, highlighting the global ecological resource advantages. The functional areas designated based on LEFs showed a good spatial correlation with the natural geographical environment. The seven biodiversity maintenance areas were mostly located at the river confluence; the two water retention areas were in the south of the Qinling-Huaihe River Line, and the six food production areas were in the central plain. In addition, the EFR process comprehensively considered the LEFs, river reaches, and provincial divisions, and it might be easier to coordinate various conflicts of interest, including economic development and ecological protection, cross-administrative regions, and adjacent functional areas.
